Design rules and essentials
The most important rule when designing a small parts assembly process is to keep it simple. Don’t try to automate so much that the machine, controls and operating procedures become complex, inconsistent and unreliable. Simplicity is essential for a reliable assembly process with minimal downtime.
Good DFA and DFM practices
Follow good Design for Automation (DFA) and Design for Manufacture (DFM) practices. Design the parts to be automatic assembly friendly. A DFA-ready part will allow your automation machine builder to design and build a machine that will reduce costs, increase uptime and reliability, decrease assembly time and increase production volumes.
Minimize your parts
Minimize the number of parts as much as possible. Minimizing the number parts has a cascading effect that results in minimizing everything from the number of motions within the machine to number of stations and number of feeding systems. These reductions result in significant cost savings.
Parts feeding: reliability
Ensure that all parts can be fed and handled economically and reliably. Consult with your automation machine builder early in the design process to evaluate feeding, gripping, moving, and releasing parts. Minimize orientation changes as each part goes through the assembly process. A bottom-up, stacked assembly is highly preferred.
Look for opportunities to prevent mistakes
Make it impossible for an operator to load a part incorrectly; don’t rely on training. Use mechanical poke yokes for part nests to maximize part location and orientation reliability.
Eliminate difficult insertion operations. Ensure that parts can be positioned and aligned quickly.
Allow reasonable tolerances and clearances. Even if available machinery can accommodate tight tolerances and clearances, they add complexity, decrease speed and increase chances of error.
Prioritize reliability. To minimize downtime and increase the return on an automation investment, ensure that reliability is the determining factor when choosing between options. Avoid methods are known to be unreliable. For example, timer-based control of motions and gravity feeders are not recommended due to reliability issues. Cylinder-mounted sensors can also be unreliable.
Minimize vibration
For example, with automatic feeding, isolate parts at the end of the feed track to remove all vibration from the part before performing a pick and place operation. Place larger vibratory feeding bowls on their own pedestals to limit vibration transfer into the machine.
Consider the environment. Will the machinery need to withstand extreme heat? What happens if the temperature exceeds tolerances on the machinery? What humidity level is required? Will the machinery be exposed to particulates? What level of lighting is required? Note that while an automated factory is sometimes referred to as a “lights out” facility, if you’re using machine vision, proper lighting will be an important consideration.
Respect space constraints. How much floor space is available? Is there enough work space to accommodate the movement of robotic arms? Do any of the spaces need safety equipment to allow humans to work nearby?
Meet or exceed key production requirements. For example, if you need a 6-second cycle time, you can’t have 10-second automation.
Select the best robot
Select the robotic system that best suits the process. Consider payload, torque, speed, precision, and tooling. Could a dual-arm robot be used to do two picks at once? When incorporating robotic systems into the design, keep in mind that the robot controller is not intended to be a cell controller.
Adhere to safety guidelines. Ensure that any collaborative workspaces are safe. Check current local and national safety regulations, electrical codes, life safety codes, and fire codes.
Double-check all assumptions. Make sure the power supply meets requirements and that the air pressure required is well under the plant specifications. E.g. design for 60psi if the plant claims to have 80psi.
Plan for the unexpected. Think of what might be needed, and how the assembly process could be designed for flexibility. Consider possible future applications.
Simplify setup and maintenance requirements. How much training and expertise will be required to teach machine operation, timing, flow, and maintenance?
With an optimized design, automated assembly can have a significant impact on reducing product cost and increasing reliability.
If you are looking to purchase a special machine, need custom automation or to learn more about how automation can help you become more successful, contact Ehrhardt Engineered Systems at 877-386-7856 or email us at sales@ehrhardtsolutions.com